Regular expression to convert urls to hyperlinks in .Net

http://www.somesite.com/default.aspx

<a href="http://www.somesite.com/default.aspx">http://www.somesite.com/default.aspx</a>

http://www.somesite.com/files/default.aspx?id=a78b38ae723b1f8ed232c23de7f9121d&n=93b34a732e074c934e32d123de19c83d

<a href="http://www.somesite.com/files/default.aspx?id=a78b38ae723b1f8ed232c23de7f9121d&n=93b34a732e074c934e32d123de19c83d">http://www.somesite.com/files/default.aspx?id=a78b38ae723b1f8...</a>

http://www.somesite.com/files/default.aspx?id=a78b38ae723b1f8...

public static string Replace(
    string input,
    string pattern,
    MatchEvaluator evaluator
)

string displayText = url.Substring(0, maxLength);
string hyperlink = string.Format("<a href="{0}">{1}</a>", url, displayText);